My supplier deducted amounts I owed from my invoice to them. how do I record those amounts (expenses) and how do I keep track of what I owe the supplier?

Hi flyingmhorses,

Making sure you're recording your transactions the right way is a good exercise for preventing errors in your books. I'd be happy to steer you in the right direction so you can focus on doing the things you enjoy. 

To ensure accuracy in your books, I recommend contacting an accounting professional to get more info on recording the transactions. Doing this will help prevent any future discrepancies in your books. If you're not in contact with one, I encourage you to search for one on our website using this link here. In the meantime, I recommend using the Expenses by supplier summary report to check your total expenses for each supplier. To find this report click Reports from the left menu > enter the report name in the search field and customize the report as you please. 

I'll also leave this question here so other accounting professional members can chime in. Let me know if you have other questions. I'm here to help.